The present invention relates generally to loader type vehicles and in particular to a bucket assembly for a front end loader.
Loaders, whether they be of the tractor or wheeled variety, are conventionally employed in excavation to haul, dig or lift earth and refuse. Typically, a loader includes a boom assembly pivotally mounted to one end of the vehicle for raising and lowering a loading bucket.
The dump height of a loader is the maximum vertical distance attainable between the ground and the leading edge of the bucket, when the boom is raised and the bucket is in its full dump position. This maximum distance is governed primarily by the length of the boom and to a lesser extent by the location of the pivot point of the bucket. The bucket is emptied of its contents by rotating it about a horizontal axis until the outward or leading edge is below the bottom of the bucket. The position of the rotational axis of the bucket will determine the final maximum dump height for a given boom length. If the axis is located near the bottom of the bucket, dump height will be reduced because the leading edge will travel downwardly a substantial vertical distance in order to accomplish the dump. If the axis is located near the leading edge of the bucket, the bottom of the bucket is raised until it is above the leading edge and the dump height is at a maximum.
Loading vehicles available from original equipment manufacturers are generally supplied with fixed boom lengths and bucket capacities for a given size vehicle. In a front end loader, a fully loaded bucket genrates a substantial moment or tilting force about the axis of the front wheels. This force is a function of the weight of the load and the length of the moment arm, that is, the horizontal distance between the front wheel axis and the center of gravity of the loaded bucket. In order to maintain vehicle stability, the loaded bucket must be adequately counterbalanced and thus, boom length and bucket capacity can not be arbitrarily selected. Consideration must be given to the vehicle weight and to the expected moment forces generated by the loaded bucket which tend to tilt or even overturn the vehicle.
With present constructions, a higher dump height can be achieved either by purchasing a larger vehicle or resorting to after-market attachments or modifications. The first choice may be unacceptable because of high cost. The second alternative may not be practical because modifications to the boom and bucket can result in a cumbersome operation and instability of the vehicle.
As discussed above, the bucket capacity and boom length must be selected in accordance with the gross vehicle weight in order to preserve vehicle stability. After market modifications that include a boom extension must provide compensation for the added moment forces generated by the increased moment arm and avoid detrimentally affecting the handling and stability of the vehicle. The boom extension increases the horizontal distance between the center of gravity of a loaded bucket and the front wheel axis and thus, the moment forces tending to overturn the vehicle are increased. To compensate for these increased forces, additional counter weight way must be provided or alternately, the load capacity of the bucket must be decreased.
Another possible vehicle modification to increase dump height is the relocation of the bucket pivot point, the object being to minimize the downward travel of the leading edge of the bucket. As noted above, this can be accomplished by locating the pivot near the leading edge so that the bottom of the bucket is lifted above the pivot point to accomplish the dump. This modification generally requires a substantial change in the bucket operating linkage and in one known case, requires the replacement of fixed OEM linkage with variable extension, fluid operated actuators. An additional operator-actuated hydraulic control is necessary to effect movement of the additional actuators. The additional operator control together with the added hydraulic equipment makes this alternative method of increasing dump height objectionable.